Meanwhile, the mood at the conference has been decidedly less complimentary, with several geneticists criticizing the methods presented in the talk, the validity of the results, and the coverage in the press.

Ngun’s study was based on 37 pairs of identical male twins who were discordant—that is, one twin in each pair was gay, while the other was straight—and 10 pairs who were both gay. He analysed 140,000 regions in the genomes of the twins and looked for methylation marks—chemical Post-It notes that dictate when and where genes are activated. He whittled these down to around 6,000 regions of interest, and then built a computer model that would use data from these regions to classify people based on their sexual orientation.